1. Field of the Invention
The invention pertains to a method and apparatus for mechanically rubblizing or breaking concrete by striking the concrete with weighted hammers with a controlled force impact, a plurality of hammers being mounted upon cantilevered spring arms.
2. Description of the Related Art
Concrete highways and other concrete structures may require replacing, and to remove existing concrete paving, floors and the like, it is necessary to break the concrete into pieces for removal and handling. Often, the concrete includes steel reinforcing bars and mesh, and the equipment used to break up concrete pavement and floors may include compressed air driven jack hammers or a heavy hammer or weight lifted and permitted to fall upon the concrete to crack the same into pieces for handling.
When breaking up concrete using heavy equipment as by gravity dropping heavy weights upon the concrete, which is a typical type of apparatus used with highway demolition, the forces imposed upon the concrete and the supporting substructure are often so great as to damage the substructure and installations buried therebelow, such as drain conduits, underground utility pipes or installation, bridge slabs, or the like.
In those instances wherein the substrata is to be protected, and the breaking of the concrete is to be closely controlled, the concrete breakage may be specified as being "rubblized". Rubblizing is a specific type of concrete demolition wherein the forces imposed upon the concrete to produce breakage are controlled so that the demolished pavement and broken pieces are not displaced downwardly, and in rubblizing, the broken concrete must be free of the reinforcement located therein, and the sizes of the concrete particles, after rubblizing, are usually no greater than approximately eight inches in dimension. Rubblized concrete may be rolled and compacted and remain in place as a base for newly poured concrete pavement and floors in view of the small particles provided. Proper rubblizing to meet specifications cannot be mechanically produced by the dropping of a conventional heavy weight upon concrete, and the use of conventional drop hammers is not practical for rubblizing in that the size of the particles required are smaller than can be effectively and efficiently produced by drop hammer type breakers.
Presently, most concrete rubblizing is produced by powerful sonic vibrators generating sonic vibrations in the rigid concrete which will pulverize the concrete, free the reinforcing steel therefrom, and produce the small size particles desired. However, sonic vibrations can only be applied to limited areas of the concrete at a given time, and rubblizing by sonic equipment is slow, expensive, and unreliable as the sonic generators require constant maintenance.
Rubblizing by a mechanical hammer wherein the impact imposed upon the concrete structure can be closely controlled is known, and the demolition hammer shown in U.S. Pat. No. 4,984,639 is capable of mechanically rubblizing concrete. The demolition hammer shown in this patent consists of a cantilever spring arm having a weight at the arm outer end, and the inner end of the arm is mounted upon movable structure, such as a backhoe, wherein the movement of the arm and hammer may be hydraulically controlled and regulated, and in this manner, the impact forces imposed upon the concrete are closely controlled. Because of the mounting of the hammer upon a spring arm, high frequency vibrations are imposed upon the concrete which produce a rubblizing action. However, the apparatus shown in U.S. Pat. No. 4,984,639 is usually not used for concrete rubblizing purposes in that it is too slow and tedious as each hammer blow must be aimed and regulated, and a high production of concrete rubblizing cannot be achieved with the apparatus disclosed.
It is known to mount a plurality of hammers or breaking heads upon concrete breaking apparatus or similar equipment, and typical devices of this type are shown in U.S. Pat. Nos. 2,350,223; 2,425,018 and 2,903,949. However, such devices are not suitable for high production concrete rubblizing, and the hammers of such devices are not related to each other in such a manner to permit the breaking impact vibrations produced by one hammer at its impact zone to be effectively transferred to the impact zone of an adjacent hammer wherein a high production concrete rubblizing operation can be achieved.